Housing for an electronic device in microwave technology

ABSTRACT

The invention relates to a housing for an electronic device in microwave technology, which is comprised of three tightly connected parts ( 2, 8, 11 ). A middle part ( 2 ) is comprised of a metal plate to which at least one circuit board ( 6, 7 ) can be attached and recesses are provided which, together with the at least one circuit board ( 6, 7 ), can produce chambers ( 4, 5 ) into which the components of the one electronic circuit protrude. Furthermore, a plastic bottom part ( 8 ) with a connector device ( 9 ) and a plastic top part ( 11 ) are provided which likewise produce chambers ( 12, 13 ) for electronic and/or microwave components.

BACKGROUND OF THE INVENTION

The invention relates to a housing for an electronic device in microwavetechnology, in particular for a radar sensor.

It is known from EP 0 685 930 A1, for example, that a radar sensor witha mount can be screwed to the exterior of a vehicle, for example inorder to measure the distance to a vehicle ahead of it. This radarsensor has an oscillator, a mixer, an amplifier, and an antenna systemfor producing and receiving radar radiation as well as a receiver withevaluation electronics. In these known apparatuses, the componentsmentioned above are installed in one or more housings which areindividually closed, as a rule very tightly, and then are fastened tothe vehicle with suitable mounts.

For the technical circuit design of the evaluation electronics, it isintrinsically known to use multilayer printed boards which are mountedin the housing, possibly with an additionally placed evaluation board.In the mount, this apparatus is then installed in the bumper of themotor vehicle, for example. The essential size of the device in thisconnection is contingent upon the separate antennas for sending andreceiving, which emit radiation through the bumper in the direction ofinterest. For space-saving reasons, the components are as a ruleaccommodated on the top between the antennas, but this can generate anundesirable leakage radiation. This requires the use of expensiveshields, for example with foam absorbers, and results in highmanufacturing costs due to the large number of parts.

SUMMARY OF THE INVENTION

In the improvement according to the invention, a housing of the typementioned at the beginning, which is for use In microwave technology,has the advantage that the housing is comprised of three parts tightlyconnected to one another, which can be made of the most favorablematerial and in terms of design, can be each be embodied optimally indetail to the components to be disposed in them.

Particularly for sensing distances and speeds by means of microwaveradar around a motor vehicle, the invention permits the production of acompact radar sensor in which the integration of antenna structures canbe advantageously designed to reduce overall dimensions. The radarsensors required for this operate in a frequency band of approximately24 GHz, offer the advantage of small antennas, and are relativelyinexpensive to produce.

The housing according to the invention is advantageously comprised of ametal plate in its middle part, to which at least one circuit board canbe attached. There are also recesses which, together with the at leastone circuit board, form chambers into which the components of theelectronic circuit can protrude. The bottom part, which is injectionmolded of plastic, has a connector device that can be contacted from theoutside. The upper part is the plastic cover which is also injectionmolded and can also, together with the at least one circuit board, formchambers for electronic and/or microwave components. The encapsulationof the components according to the invention advantageously suppressesundesirable emissions of microwave radiation.

Advantageously, the middle part is provided with centering marks whichengage in corresponding marks on the bottom part and on the cover duringassembly and to simplify production, the middle part can also besymmetrically designed.

In order to attach circuit boards to the middle part, it can also beadvantageously provided with recesses and mounting points; depending onthe components required, one or two circuit boards can be provided, forexample an upper and a lower one. The circuit details with the antennastructures must be placed on the upper circuit board due to the emissionof microwaves. Multilayer circuit boards equipped on one or both sides,which are made of composite materials or multilayered ceramics, can beused in this connection, whose connections must be contacted, e.g.bonded, before the lower connector part is mounted onto the bottom. Inanother work step, the upper circuit board can be bonded; in thisinstance, a favorable disposition of contacts arranged in a row does notrequire any large travel distances.

The lower connector part of the housing according to the invention hasthe required number of connector contacts and a connector form adaptedto the respective intended use; the connector contacts are injectionmolded in place and can be glued to the metal plate when being assembledwith the middle part. As a result, the bottom part of the housing, whichis comprised of the middle part and the lower connector part, can beclosed in a watertight fashion where additional clips can produce anadjustment and can prevent a shifting before the gluing.

The cover of the housing according to the invention is designed in aparticularly advantageous manner for encapsulating the individual units,such as antennas, oscillator, mixer, evaluation electronics, etc.. Inthe regions disposed opposite the antennas, materials are provided asso-called optical windows to improve the transmission of microwaves andin the other regions, materials are provided to absorb microwaves.Consequently, several functions are integrated into the plastic cover ofthe housing in a simple manner.

A first advantageous embodiment for producing these optical windows canbe achieved by clipping metal structures into the corresponding chamberson the cover. In addition, a flat ceramic plate can also be affixedbetween the wall of the cover and the metal structures that are clippedin place.

In another advantageous embodiment, the optical windows are produced bymetal grating structures that are injection molded in place.Furthermore, the optical windows can be fundamentally comprised of aceramic plate that is metallized on one or both sides and is injectionmolded in place, where the outer side or both the outer and inner sidesof the ceramic plate is/are injection molded into the cover. Themetallizations on the ceramic plate can be connected to the ground ofthe circuit board by means of a metal spring.

For a suitable dimensioning of the chambers and parts of the housingaccording to the invention, for example at a frequency of 24 GHz, thedistances and the material thicknesses are selected in multiples of afourth of the wavelength of the microwave radiation. For example in air,the distance between the ceramic plate and the circuit board isapproximately 3 mm, the thickness of a thick-layered ceramic plate is 1mm, and the plastic is approx. 1.7 mm. The plastic coating, which can beapplied to one or both sides, is also used here as an adaptationstructure because of its dielectric constants. In order to use so-calledsuperstrate effects, the distance in air must thereby be selected to beon the magnitude of λ/2 of the microwave length, while the ceramic platemust be λ/4 thick. Through the selection of a suitable metallization ofthe ceramic plate, the desired antenna characteristics can be achievedwith only one patch as a power element in order to limit the size.

In an advantageous embodiment, the antennas are comprised of a number ofpatches, for example 2, 3, 4, or 6 of them; inwardly protrudingdielectric horns can be provided as focusing devices in the opticalwindows above these patches. It is also advantageously possible forinwardly and/or outwardly protruding dielectric lenses to be provided asfocusing devices in the optical windows.

Through the use of the above-mentioned focusing elements, circuit boardscan be advantageously used which are significantly smaller than ispossible in an apparatus with only one patch. The only requirement hereis that the plastic of the cover be microwave permeable, as is the case,for example, with polyetherimide or comparable plastics.

After complete assembly of the individual parts of the housing, thecover is consequently also glued to the combination of the lowerconnector part and the metal middle part and is therefore also closed ina watertight fashion. In order to fasten the housing, for example to thebumper of a motor vehicle, a mount is provided on at least one of thethree parts and is comprised of an extension, possibly with athickening, with elements that can be screw connected or clipped inplace. An extension and thickening of the middle part offers theadvantage of better heat dissipation; by contrast, it is less expensivein terms of manufacturing to affix the mount to the plastic bottom part.

The pressure compensation inside the housing can be executed withconventional, known pressure compensation elements; a pressurecompensation is also possible inside the connector and via the coppercores of the companion part plugged into it. The proposed housingaccording to the invention is suitable not only for building a radarsensor but also for building communications devices and other sensorswhich use microwaves in a frequency range of up to 140 GHz. Thegeometries of the housing simply need to be adapted to the componentsrequired and the wavelengths used.

In addition to the claims, these and other characteristics of proposedimprovements of the invention can also be inferred from thespecification and the drawings; the individual characteristics can berespectively produced in and of themselves or combined in the form ofsub-combinations in the embodiment of the invention, can be produced inother areas, and can represent intrinsically patentable embodimentswhich are claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of a housing according to the invention for anelectronic device in microwave technology are explained in conjunctionwith the drawings.

FIG. 1 is a section along a longitudinal line through the principalstructure of a housing of this kind;

FIG. 2 is a section through an exemplary embodiment which, in contrastto FIG. 1, is provided with metal clips in the optical window of theantenna system in the housing;

FIG. 3 is a section along a lateral line of the exemplary embodimentaccording to FIG. 2;

FIG. 4 is a section through an exemplary embodiment which, in contrastto FIG. 1, is provided with a metal structure injection molded into theoptical window of the antenna system in the housing;

FIG. 5 is a section through an exemplary embodiment which, in contrastto FIG. 1, is provided with focusing devices in the optical window ofthe antenna system in the housing;

FIG. 6 is a section along a lateral line of the exemplary embodimentaccording to FIG. 5;

FIG. 7 is a section through an exemplary embodiment which, in asupplement to FIG. 1, is provided with a mount on the bottom part of thehousing and

FIG. 8 is a section through an exemplary embodiment which, in asupplement to FIG. 1, is provided with a mount on the middle part of thehousing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a housing 1 for a radar sensor as a microwave device, whichcan be fastened to a motor vehicle, for example to the bumper, in such away that it can emit electromagnetic waves for distance sensing. Thehousing 1 has a middle part 2 which is comprised of a metal plate and isprovided with centering marks 3 for adjusting the other housing partsand is provided with recesses or chambers 4 on the one side and withrecesses or chambers 5 on the other side. The chambers 4 and 5 can, forexample, be symmetrically disposed; circuit boards 6 and 7 are disposedin the chambers 4 and 5 and are connected to the middle part 2 by meansof mounts that are not shown here.

In a modification of the embodiment shown in FIG. 1, the housing canalso be embodied with only one circuit board, e.g. the circuit board 6.Components of the electronic circuit, in particular also microwaveemitting components, can be accommodated in the chambers 4 and 5. Thecircuit details with the antenna structures must in any case rest on theupper circuit board 6 due to the omission of microwaves. Multilayercircuit boards equipped on one or both sides can be used as circuitboards here, which are comprised of composite materials or multilayeredceramics.

There is also a bottom part 8, preferably an injection molded plasticpart, which has a connector device 9. This part 8 has recesses in whichthe markings 3 of the middle part 2 can engage and the position of theparts 2 and 8 is consequently fixed and in addition, a tight reciprocalfit is possible. The connections on the circuit boards 6 and 7 must becontacted, e.g. bonded, possibly also with through contacts 10, beforeinstallation of the lower connector part 8 onto the bottom. Theconnector contacts of the connector device 9 can be injection moldedhere and can be glued to the middle part 2, i.e. to the metal plate.

In addition, in the exemplary embodiment according to FIG. 1, an upperpart 11, preferably also an injection molded plastic part, is providedas a cover, which likewise has recesses in which the markings 3 of themiddle part 2 can engage and consequently the position of the parts 2and 11 is fixed and sealed in the same way as the assembly of the parts2 and 8. Chambers 12 and 13 are also embodied in the upper part 11 andindividual units such as antennas, oscillators, mixers, and evaluationelectronics can protrude into these chambers.

In the regions 14 and 15 disposed opposite the antennas, there areso-called optical windows in the plastic part 11 according to FIG. 1,which contribute to an encouragement of the transmission of microwaves.In the other regions of the part 11, the materials are disposed so thatthey are suited for the adsorption of microwaves. The optical windowscan, for example, be comprised of a flat ceramic plate 11 that isinjection molded in place and is metallized on one or both sides; theouter side or both the outer and inner sides of the respective ceramicplate 17 is/are injection molded into the region 14 or 15 of the upperpart 11. The metallizations on the ceramic plate 17, which are not shownhere, can be connected to the ground of the circuit board 6 by means ofa metal spring 18.

FIG. 2 shows another exemplary embodiment for producing theabove-mentioned optical windows in the regions 14 and 15 of the upperpart 11; components which have not been changed are provided with thesame reference numerals here as in FIG. 1. The optical windows can beproduced here by clipping metal structures 20 under a flat ceramic plate21 in the region 14 on the left and by clippling the metal structures 20directly to the plastic of the upper part 11 in the region 15 on theright. FIG. 3 also shows the position of the metal structures 20 in asection along a transverse line through the housing 1.

In an exemplary embodiment according to FIG. 4, the optical windows areproduced by means of metal grating structures 22, which have a focusingaction, being injection molded into the plastic in the regions 14 and 15of the upper part 11.

If an antenna system is designed, in a manner not shown in detail herein the Figs., in such a way that the antennas are comprised of a numberof patches, for example three of them, then according to the exemplaryembodiment in FIGS. 5 and 6, focusing devices can be affixed above thesepatches in the optical windows of the regions 14 and/or 15. In theregion 15 on the right, so-called dielectric horns 23 provided asfocusing devices protrude into the chamber 13 of the housing 1. In theregion 14 on the left in FIG. 5, inwardly and/or outwardly protrudingdielectric lenses 24 and/or 25 are provided as focusing devices in theoptical windows. The dielectric horn 23 from FIG. 5 is also shown inFIG. 6, in a sectional view along a transverse line.

FIGS. 7 and 8 show exemplary embodiments of a suitable mount forfastening the housing 1, for example to the bumper of a motor vehicle.According to FIG. 7, a mount 26 in the form of an extension of theplastic bottom part 8 of the housing 1 is proposed which, possibly witha thickening, can be screw connected by means of a bore 27 or clipped bymeans of a clip element 28. A mount 29 using an extension and thickeningof the metal middle part 2 is shown in FIG. 8; where in this instancethe screw- or clip elements 27 and/or 28 of the kind in FIG. 7 can beused.

What is claimed is:
 1. A housing for an electronic device in microwavetechnology, comprising housing parts tightly connectable with oneanother and; an electronic circuit located in the housing; microwavecomponents located in the housing and including antennas for sending andreceiving microwaves, said housing parts including a bottom part, amiddle part, and a top part, said middle part being formed as a metalplate to which at least one circuit board is attachable and which hasrecesses which, together with the at least one circuit board, formchambers into which components of the electronic circuit protrude, saidbottom part having an externally connectable connector device, said toppart being affixed as a cover, which together with the at least onecircuit board, can also form chambers for electronic or microwavecomponents, said middle part being provided with centering marks whichengage in corresponding marks of said bottom part and said top partduring assembly.
 2. An electronic circuit and microwave components asdefined in claim 1, wherein said middle part is symmetrical.
 3. Anelectronic circuit and microwave components as defined in claim 1,wherein said top part is formed so that in regions disposed opposite tothe antennas, materials are provided that serve as optical windows forencouraging a transmission of microwaves, and in other regions materialsare provided to absorb microwaves.
 4. An electronic circuit andmicrowave components as defined in claim 3, wherein said optical windowsare formed as a ceramic plate which Is Injection molded in place and ismetalized on at least one of its sides, said ceramic plate having anouter side and an inner side, such that at least one of said sides isinjection molded In place.
 5. An electronic circuit and microwavecomponents as defined in claim 4, wherein said ceramic plate hasmetallizations connected to a ground of the circuit board by a metalspring.
 6. An electronic circuit and microwave components as defined inclaim 3, wherein said optical windows are formed by clipping metalstructures in place.
 7. An electronic circuit and microwave componentsas defined in claim 6, wherein a flex ceramic plate is affixed between awall of said top part and the metal structures that are clipped inplace.
 8. An electronic circuit and microwave components as defined inclaim 3; and further comprising metal grating structures that areinjection molded in place and provide a focusing action in said opticalwindows.
 9. An electronic circuit and microwave components as defined inclaim wherein said antennas are composed of a number of patches, andInwardly protruding dielectric horns are provided above said edges insaid chambers of said top part as focusing apparatuses.
 10. Anelectronic circuit and microwave components as defined in claim 9,wherein said antennas are composed of a number of patches; and furthercomprising dielectric lens which protrude inwardly or outwardly abovesaid patches and are formed as focusing apparatuses.
 11. An electroniccircuit and microwave components as defined in claim 1, wherein at leastone of said housing parts has a mount composed of an extension.
 12. Anelectronic circuit and microwave components as defined in claim 11,wherein said mount has a thickening with elements which can be screwedor clipped in place.
 13. An electronic circuit and microwave componentsas defined in claim 11, wherein said mount Is composed of plastic. 14.An electronic circuit and microwave components as defined in claim 11,wherein said mount is composed of metal.